Patent GB-878149-A (GB)
Title: Improvements in the preparation of photographic dye images
IPC: G03C5/315
Filed: 1957-12-02
Abstract: 878,149. Photographic dye transfer processes. KODAK Ltd. Dec. 2, 1957 [Dec. 3, 1956], No. 37465/57. Drawings to Specification. Class 98(2) An image is made in a light sensitive silver halide material having a layer of a hydrophilic colloidal binder containing a dye or colour coupler which may itself be coloured dissolved in a solvent therefor, the ratio of colloidal binder to the solvent in the layer being between 1 to 1 and 1 to 5, and then the material is pressed into contact with a receiving sheet so that dye solution is transferred in accordance with the image to the receiving sheet. In one form the colloidal binder contains no light-sensitive substance but is overcoated with a layer of silver halide emulsion, and this is exposed, developed to a relief image, and pressed into contact with an oilabsorbent support so that dye solution passes through the open spaces of the image on to such support; in another form the colloidal binder layer contains silver halide emulsion, and colour coupler with the solvent, and this layer is exposed, colour developed and similarly pressed into contact with an oil-absorbent receiving support, this time to transfer solvent containing unchanged coupler in unexposed regions of the layer and developed dye in the exposed regions. Crystalloidal solvents of boiling points above about 175‹C. are preferred. In an example of the first stated form (Example 4), a cellulose ester film base is coated with an aqueous mixture comprising a specified dye, diethyl lauramide and gelatin, and overcoated with a silver chloride emulsion containing 4-phenyl catechol as tanning developing agent, the emulsion is exposed to a high contrast positive transparency, processed for 20 seconds in a solution containing sodium carbonate and urea, and passed three times in contact with an unsized paper stock through a pair of pressure rollers to remove untanned gelatin, after which up to 10 transfers can be made to separate sheets of paper to produce a dye image by squeezing dye through areas where the untanned gelatin had been removed. The second form has three examples, in the first (Example 1) a similar film base is coated with a gelatino-silver chloride emulsion containing a specified cyan coupler and di-n-butyl phthalate, exposed to a negative subject, colour developed, and pressed firmly on to a sheet of writing paper to effect transfer of solvent containing dye in the images areas but only unreacted coupler in non- image areas. In the next (Example 2) a red sensitive chlorobromide emulsion otherwise similar to that of Example 1 is coated on to film base and overcoated with a green-sensitive/magenta coupler emulsion of similar type, exposure is effected separately to a line subject through a green and red filter, and development is effected as in Example 1, the material is treated in a stop bath of a saturated solution of sodium sulphate containing acetic acid, wiped dry and pressed on to photographic paper to transfer a line image of magenta and cyan dyes; the receiving sheet is then washed to remove any unreacted developer. In Example 3 a gelatino-silver chloride emulsion containing cyan, magenta and yellow couplers and di-n-butyl phthalate is exposed through (a) a continuous tone step wedge, (b) a line negative and (c) a half-tone positive, processed in the developer of Example 1, wiped dry and pressed on to photographic paper to transfer a continuous tone, a sharp line, and a sharp half-tone image respectively in neutral dye. Preparations of the layer materials, developers, times of treatment and such like are fully described in the examples; and the Specification concludes with data concerning desirable ratios between gelatin, coupler, and coupler solvent weights, and pressures and transfer times for effective image transfers. Instead of the coupler solvents referred to above a high melting point hydrocarbon wax may be used, but in this case heat as well as pressure must be used to obtain image transfer. Specifications 541,589, 627,814, 655,274, 680,488, 791,219, 800,108 and 843,497 are referred to.